Does fracking cause earthquakes in BC?

The CBC recently published an article on two large, fracking-induced earthquakes near Ft. St. John, BC. One was magnitude 4.6 and the other magnitude 4.7, and these are strong enough to shake your house and the belongings in it. I am asked regularly about the dangers of fracking, and these events are a good reason to discuss the positives and negatives of fracking for British Columbia.

Why Frack?

That is a good question. Oil and gas (hydrocarbons) are produced from tiny pore spaces, or holes, that exist between grains of sand and mud that make up sandstone and mudstone. At 2 km depth or more, if there is enough connection between the holes in the sandstone or mudstone, then hydrocarbons flow through the rock towards the vertical wells drilled to produce them. In rocks where the holes in the rock are not connected, companies need to drill wells horizontally and then frack the wells multiple times (known as multi-stage fracking) to produce the hydrocarbons. Think of the rock with unconnected holes as being a bit like a cement sidewalk - they are extracting hydrocarbons from that. Check out the video below on how multi-stage fracking works most of the time. The photos below the video show the types of rock and size of the holes that store the hydrocarbons accessed through multi-stage fracking.

The two photos on the left are of pieces of rock extracted from the Montney Fm in northeast BC, but from >2,000 m below ground. There are tiny holes between the grains of sand (light gray) and mud (dark gray) where natural gas is stored (image source: 1). The cube on the right is a close up of a tiny piece of rock showing an example of the size of holes (dark areas) that store gas. For reference, 1,000 microns = 1 mm so this rock chip is < 0.01 mm in each direction (image source: 2).

Benefits of fracking

The benefits of fracking for BC are in employment, energy security, and government revenue. Since 2007, northeast BC has been a hotbed of horizontal drilling and multi-stage fracking. Hydrocarbons produced using these technologies dominate production in BC (see graphs below). The BC government takes a 5% royalty from each well drilled for the first 12 months, and then applies a royalty rate between 5 and 40%, based on the value of the hydrocarbons produced (e.g., price of natural gas versus oil). They also receive income tax from producers, companies, and individuals who work in or for the petroleum industry, and this results in billions of dollars in revenue for the BC government. Jobs in the petroleum industry are also well-paying, and gas produced in northeast BC is the main natural gas supply for residents of the Lower Mainland BC and for much of Washington State, USA.

Top: The number of wells drilled in BC has not changed much over time, but the number of fracture stimulations has. This is a result of horizontal drilling and multi-stage fracking. Bottom left: The two blue colours indicate natural gas production from wells that need only a minor amount of fracture stimulation. The green and purple colours are production from wells using horizontal wells and multi-stage fracking, and this has become the dominant hydrocarbon source since 2010. Bottom right: The "Montney" and "Horn River Basin and Liard" parts of the pie show that nearly 75% of all the hydrocarbons in BC must be accessed using multi-stage fracking. (Source of all images: 3)

Dangers of fracking

While there are benefits to fracking, there are also some serious drawbacks. First amongst these is induced seismicity or man-made earthquakes. When companies fracture the rock, they do so with pressurized fluid. If that fluid enters an existing fault or crack in the rock, it lubricates the rock and props open the crack allowing the rock to move. This produces an earthquake.

Left: Map of horizontal wells and small earthquakes that formed around the wells (small gray and orange bubbles; image source: 4). Right: Cross section (like looking at a wall) of the same wells below ground. The colour dots show where small (nearly imperceptible) tremors were recorded as the rocks were fracture stimulated.

Most multi-stage fracking activity does not induce earthquakes, but greater than 2.5% do and that is a problem. Most induced earthquakes are small (less than magnitude 3.0; 3), but when they exceed magnitude 4, it is worrying (see graphs below). Government scientists have identified areas of higher risk for inducing earthquakes, but so far little has been acted upon. I expect we will continue to hear about these events in the news until the government develops guidelines and enforces rules. In the meantime, let's hope no one is hurt from one of these events.

Human-induced earthquakes resulting from disposal of water underground (left) and from hydraulic fracturing (right)(images source: 3).

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Info Sources:

1) Nadaraju, G. and Elliot, D. 2010. Understanding Montney reservoir heterogeneity: A

geo-engineering approach. Encana Corporation.

2) Bai, B., Elgmati, M., Zhang, H., and Wei, M., 2013, Rock characterization of Fayetteville shale gas plays: Fuel, v. 105, p. 645-652.

3) BC Oil and Gas Commision. 2014. Investigation of Observed Seismicity in the Montney Trend. 32 p.

4) BC Oil and Gas Commission. 2012. Investigation of Induced Seismicity in the Horn River Basin. 29 p.